WebApi MapHttpAttributeRoutes causes error in IComponent

[Padbury]

This is similar to issue #4464 but slightly different hence the new issue.

So, in v7 to register my own WebApi routes I'd create a class that implements IApplicationEventHandler and register my routes via the OnApplicationStarted method like this:

GlobalConfiguration.Configuration.MapHttpAttributeRoutes();

In v8, it's suggested to use a class that implements IUserComposer then append a component. Then it's suggested to use the Initialize() method to execute startup functions.

However, if I put GlobalConfiguration.Configuration.MapHttpAttributeRoutes(); inside Initialize() I get the following error:

The object has not yet been initialized. Ensure that HttpConfiguration.EnsureInitialized() is called in the application's startup code after all other initialization code.

If I move the call into the constructor for the class

public RouteConfigComponent() { GlobalConfiguration.Configuration.MapHttpAttributeRoutes(); }

Then the error goes away and routes are registered correctly using attributes e.g.

[Route("api/question/{id}")] public HttpResponseMessage Get(int id) { return Request.CreateResponse(HttpStatusCode.OK); }

The workaround is to have this in the constructor but I'm told this is probably not the desired behaviour and to register it here for review.

[zpqrtbnk]

Notes for self: odd that it works in the constructor and not in Initialize as Initialize runs after the constructor. Going to look into it.

[zpqrtbnk]

Reproduced. Putting MapHttpAttributeRoutes in the Initialize method does trigger the exception.

[zpqrtbnk]

The problem is caused by WebRuntimeComponent doing:

// ensure WebAPI is initialized, after everything
GlobalConfiguration.Configuration.EnsureInitialized();

in its own Initialize method - and we do need to do this for everything to run.

But because your component runs after the WebRuntimeComponent, it invokes MapHttpAttributeRoutes after EnsureInitialized has been invoked, hence the exception.

Short term, registering your component as follows would work:

public class MyComposer : IComposer
{
  public void Compose(Composition composition)
  {
    composition.Components().Insert<TempComponent>();
  }
}

because it would insert your component in the first position, ie even before WebRuntimeComponent - but then, you have to be careful with what you do in the component, as strictly nothing will be initialized (no content cache, no nothing).

Longer term, it feels that EnsureInitialized should run after every other component has had a chance to do things - not before. Looking into it.

[zpqrtbnk]

Going to fix it properly - in progress.

[zpqrtbnk]

PR: #4856

Test: with this in place, a user component should be able to MapHttpAttributeRoutes because EnsureInitialized will run last (after every other components).

Note: renaming some composers etc = breaking.

[Shazwazza]

I can confirm this works. The breaking names are not going to affect anyone ... well except for @aaronpowell ;)

[aaronpowell]

Haha I think I'm good for this one 😛